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Motorola SL300 - need to wait after power down before will charge?

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g8tzl2004
Posts: 1099
Joined: Wed Sep 08, 2004 10:13 am

Motorola SL300 - need to wait after power down before will charge?

Postby g8tzl2004 » Mon Aug 06, 2018 8:40 am

I am charging my SL300's using a standard USB charger (5v 2A) but not an official Motorola charger....actual one used to charge a tablet PC so plenty of current.

The SL300's charge OK...BUT I have found that if I have been using the SL300's, if I power down and immediately connect the charger, I get a voice annoucement saying "unable to charge" or something similar. But if I wait a few minutes after powering down and then connect the charger it charges OK.

Anybody know what is going on? Maybe the battery voltage under load is too low and you need to let it recover after powering down...but then you would never be able to recharge a flat battery. Is there anything special with the official Motorola USB charger?

sjxts3000
Posts: 875
Joined: Sat Jul 09, 2011 8:14 pm
What radios do you own?: APX

Re: Motorola SL300 - need to wait after power down before will charge?

Postby sjxts3000 » Mon Aug 06, 2018 1:25 pm

How about you just use the dang charger that came with the radio? You spend several hundred dollars on each of your radio*s* (you said plural) and then use some other $10 charger to charge them?

VE3TUH
Posts: 261
Joined: Fri May 24, 2002 3:14 pm
What radios do you own?: more than I should...

Re: Motorola SL300 - need to wait after power down before will charge?

Postby VE3TUH » Sun Aug 12, 2018 6:55 am

Did you test with the proper charger to see if this behaviour is consistant or just related to your aftermarket charger? And no, you shouldnt have to power down to charge the battery. However, a friend of mine has an SL300 with similar charging issues.

g8tzl2004
Posts: 1099
Joined: Wed Sep 08, 2004 10:13 am

Re: Motorola SL300 - need to wait after power down before will charge?

Postby g8tzl2004 » Fri Aug 24, 2018 4:07 pm

I got the SL300's real cheap from a junksale - seller must have thought that they were FRS type radios - they sort of look a bit like FRS radios but are actually great performers. However the radios did not come with an OEM Motorola micro USB charger...but USB chargers are meant to be "standard"...5v at 500mA?

I'm using an 5v 2A USB charger from a Tablet (but I've tried other chargers)...so plenty of amps available...although maybe its only 1A even though it says 2A...although the USB standard says max current draw should only be 500mA??

I'm thinking that maybe the issue is something to do with voltage drop perhaps due to thin wiring in the USB cable. Maybe the SL300 tries to charge at 2A but this results in too much load for the thin cable wiring (designed for 500mA max?) and the voltage under load then drops below 5v and you get the warning?? But I'm still not sure why I get the warning immediately after powering down but its OK if I wait a few minutes??

OK on others having the same problem. Maybe its a firmware issue and the firmware needs to be updated?

sjxts3000
Posts: 875
Joined: Sat Jul 09, 2011 8:14 pm
What radios do you own?: APX

Re: Motorola SL300 - need to wait after power down before will charge?

Postby sjxts3000 » Fri Aug 24, 2018 4:10 pm

The charger for my SL3550e (same battery as the SL300) is 5V @ 1A.

g8tzl2004
Posts: 1099
Joined: Wed Sep 08, 2004 10:13 am

Re: Motorola SL300 - need to wait after power down before will charge?

Postby g8tzl2004 » Fri Aug 24, 2018 4:26 pm

Maybe the radio detects that an non OEM charger is attached so gives the warning to encourage users to buy an "expensive" OEM Motorola charger :) But maybe there is a 5 minute timeout on the warning :)

Is the OEM charger identical/similar to a real Motorola micro USB cellphone charger?

Has anybody used a real Motorola micro USB cellphone charger with the SL300's....I'm wondering if I have one in my "collection".... I certainly have a mini USB Motorola cellphone charger.

sjxts3000
Posts: 875
Joined: Sat Jul 09, 2011 8:14 pm
What radios do you own?: APX

Re: Motorola SL300 - need to wait after power down before will charge?

Postby sjxts3000 » Fri Aug 24, 2018 4:29 pm

I've used a micro-USB to USB-A cable and plugged it into my PC (for programming) and it does charge the radio, through slowly (it's just USB 2.0) No warnings on radio about a lower power charge source, though.

g8tzl2004
Posts: 1099
Joined: Wed Sep 08, 2004 10:13 am

Re: Motorola SL300 - need to wait after power down before will charge?

Postby g8tzl2004 » Sat Aug 25, 2018 5:38 am

Did you use an OEM Motorola programming cable or just a standard micro to USB A cable?

sjxts3000
Posts: 875
Joined: Sat Jul 09, 2011 8:14 pm
What radios do you own?: APX

Re: Motorola SL300 - need to wait after power down before will charge?

Postby sjxts3000 » Sat Aug 25, 2018 6:02 am

g8tzl2004 wrote:Did you use an OEM Motorola programming cable or just a standard micro to USB A cable?

Standard. It’s actually a cable from an Anker portable battery charger. Micro-USB to USB-A


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